1. Field of the Invention
The present invention relates to an Ethernet-to-serial gateway apparatus for Internet Protocol (IP) multicasting and a method thereof. More particularly, the present invention relates to a gateway apparatus and a method that may effectively transmit IP multicasting data via a serial interface.
2. Description of the Related Art
Many ship apparatuses such as a navigation apparatus and sensors within a ship may exchange information through a communication mechanism performing a message exchange based on American Standard Code for Information Interchange (ASCII) such as National Marine Electronics Association (NMEA) 0183 via a serial interface such as Recommended Standard (RS) 485.
However, due to a new paradigm such as e-navigation, an amount of information exchanged between apparatuses on a ship is currently increasing. Accordingly, instead of a low speed serial interface, a use of a high speed Ethernet interface greater than or equal to 100 Mbps is increasing.
Accordingly, a function about an Ethernet-to-serial gateway performing a transformation functionality between the high speed Ethernet interface and the low speed serial interface, and between an Internet-based protocol and an NMEA 0183-based protocol has become important.
In the case of a ship navigation apparatus based on a serial interface, basically to obtain information required for a single ship apparatus, apparatuses desiring information may obtain the information through a one-to-one connection with other apparatuses providing the information.
This indicates that N serial interfaces may need to be provided to transfer information to N apparatuses in the single ship apparatus. Specifically, the same data may need to be copied and be provided to the N serial interfaces.
The above one-to-N communication scheme may be easily performed in an Ethernet-based Internet Protocol (IP) network through IP multicasting. Specifically, when apparatuses desiring particular information are grouped into a single group and apparatuses belonging to the same group share a single IP multicasting address, information exchange between the apparatuses having the same IP multicasting address may be performed using a single transmission.
However, on a ship with an Ethernet-based IP network, all the apparatuses are generally connected to the same subnet. Therefore, when IP multicasting is performed, all the apparatuses included in the same network may receive the same data, similar to broadcasting.
In particular, when an Ethernet-to-serial gateway apparatus connected to a plurality of apparatuses via respective corresponding serial interfaces does not provide a particular filtering mechanism, data may be transmitted to all the apparatuses via all the serial interfaces. Consequently, data may be transmitted to an undesired apparatus, which may result in causing overhead, thereby deteriorating a transmission efficiency.
Even though some of navigation information needs to be sequentially received, a plurality of pieces of navigation information may be periodically transmitted. Accordingly, reliable and sequential information may not be required at all times.
In particular, when information is transferred via a low speed serial interface, overflow may occur in a buffer due to a large amount of information received via a high speed Ethernet interface. In the case of the above navigation information, most current information should be safely transmitted first than previously transmitted information. However, in the case of a queuing scheme using a simple last-in-first-output (LIFO) scheme, old navigation information may be transmitted after the latest navigation information is transmitted, which may be inappropriate.